Tobacco treatment

ABSTRACT

The invention relates to a method of treating tobacco to reduce or eliminate nitrosamines therefrom. The method comprises the use of a supercritical fluid extraction medium at elevated temperature and pressure to selectively remove nitrosamines compared with nicotine removal. The nitrosamnine content for all tobacco types can be reduced.

[0001] The present invention relates to a method of treating tobacco toreduce or eliminate the content of nitrosamines therein, particularlytobacco specific nitrosamines,

[0002] Tobacco specific nitrosamines include N′-nitrosonornicotine,4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, N′-nitrosoanatabine andN′-nitrosoanabasine.

[0003] Various methods are known for the removal of nitrosamines fromtobacco. In U.S. Pat. No. 5,803,081 and WO 98/58555 green leaf tobacco(i.e. tobacco prior to curing) is subjected to microwave radiation,convection heating or freeze drying in order to kill microbes thought tobe responsible for the production of nitrosamines during curing of thetobacco. A disadvantage of this method is that the method includes therequirement of specific curing practices for the tobacco, which curingpractices are carried out on the tobacco at an early stage post-harvest.

[0004] An aim of the present invention is to provide an improved methodfor reducing nitrosamines in tobacco.

[0005] A further aim of the present invention is to provide an improvedmethod for selectively reducing nitrosamines in tobacco.

[0006] The present invention provides a tobacco treatment processwherein tobacco is subjected to treatment with a supercritical fluidextraction medium to extract nitrosamines from said tobacco.

[0007] Preferably, nitrosamines are separated from the supercriticalfluid extraction medium by subjecting the extraction medium to anitrosamine removal process.

[0008] Suitably, the nitrosamine removal process may comprise achemisorption step. Preferably, the chemisorption step may comprise theuse of an ion exchanger.

[0009] Alternatively, the nitrosamine removal process may comprise anadsorbent step. A suitable adsorbent may be selected from one or more ofthe group consisting of glass beads, activated charcoal, aluminiumsilicate and zeolites. Other suitable adsorbents known to those personsskilled in the art may also be used.

[0010] In a further alternative, the nitrosamine removal process maycomprise treatment of the extraction medium with ultraviolet (UV) light,resulting in the breakdown of nitrosamines in the extraction medium.

[0011] Yet further alternatives include the removal of nitrosamines byprecipitating the nitrosamines from the extraction medium; by subjectingthe extraction medium to nitrosamine specific enzyme breakdown; or bychromatographic or other methods of separation known to those personsskilled in the art.

[0012] The process for nitrosamine removal from the extraction mediummay comprise more than one of the above outlined nitrosamine removalprocesses. In certain circumstances, at least, use of a plurality ofremoval processes (together comprising a multi-process) will result inan enhanced specificity of removal of nitrosamines. For example, thenitrosamine removal process may be a multi-process comprising achemisorption step in combination with or followed by treatment with UVlight. Prior to the UV light treatment a washing step may be required toremove the nitrosamines from the chemisorption medium, the UV light thenbeing applied to the washings. Water, an acid, a salt solution or analcohol may suitably be used in the washing step.

[0013] Suitably, the extraction medium having had some, if not all, ofthe nitrosamines removed therefrom may be brought into contact withtobacco, such that extract(s) other than nitrosamines in the medium maybe incorporated or re-incorporated with the tobacco. Such extract(s)may, for example, comprise nicotine and/or flavour substances.

[0014] Much by preference, the supercritical fluid used is supercriticalcarbon dioxide, although other supercritical fluids known to the skilledperson may be suitable.

[0015] Suitably, an acid, preferably an organic acid, may be added tothe tobacco prior to treatment of the tobacco with supercritical fluid.Alternatively, the acid may be incorporated with the supercriticalfluid. Furthermore, when an ion exchanger or adsorbent material ispresent, the acid may be incorporated with the ion exchanger oradsorbent. A suitable acid may be an organic acid selected from one ormore of the group consisting of malonic acid, ascorbic acid, succinicacid, glutaric acid, adipic acid, malic acid, tartaric acid, mucic acidand citric acid, or a salt derivative(s) thereof. Preferably, theorganic acid is a citric acid salt, potassium citrate for example. Othersuitable acids may be mineral acids, for example sulphuric acid andphosphoric acid. Suitably, when the acid is applied to the tobacco theacid is in solution. Such solution may be applied by spraying.Advantageously, the application of the acid to the tobacco may takeplace in a casing cylinder conventionally used within the tobaccoindustry for applying casings to tobacco.

[0016] Other modifiers, such as organic solvents or alcohols, forexample, may alternatively or additionally be used.

[0017] Preferably, the extraction treatment of the tobacco with thesupercritical fluid takes place at an elevated pressure and temperature.Suitably, when the supercritical fluid is carbon dioxide a pressure inthe range of 100 to 350 bar may be used, preferably the pressure beingabout 200 to 300 bar and more preferably being about 240 to 260 bar.Preferably, the temperature used is greater than about 350 Celsius, morepreferably in a range of about 35 to about 140° Celsius, and even morepreferably in a range of about 35 to about 90° Celsius.

[0018] Advantageously, the tobacco is placed in a closable chamber orbomb during the extraction treatment thereof with the supercriticalfluid.

[0019] Heating may be effected by heat transfer or by electromagneticradiation (i.e. microwave or radiofrequency heating). Whenelectromagnetic radiation is used the closed chamber or bomb will, ofcourse, have to be made of a non-electromagnetic absorbing material,e.g. non-metallic material, capable of withstanding the operatingpressure. A suitable such material may be comprised of apolyfluorohydrocarbon material, such as Teflon (Trademark) for instance.

[0020] The technical effect of removing tobacco specific nitrosamines byprocessing of tobacco with supercritical fluid was heretofore unknown.Much by preference the conditions at which the extraction treatment ofthe tobacco with the supercritical fluid takes place are biased towardsextraction in the supercritical fluid of nitrosamines, as compared withother tobacco specific compounds, such as nicotine for instance.Advantageously, no or very little, nicotine is removed from the tobaccoin the extraction medium. Conditions which favour nitrosamine extraction(compared with nicotine extraction) include a pH of the tobacco of lessthan about 6.5, and preferably less than about 5.5.

[0021] Preferably, the ratio of the percentage reduction in nitrosaminesto the percentage reduction in nicotine in tobacco, which tobacco hasbeen subjected to the process of the present invention, is in the rangeof about 1.1:1 to about 18:1, more preferably about 1.3:1 to about 10:1,and even more preferably about 2:1 to about 6:1.

[0022] For a given set of treatment conditions, including, for example,the mass flow rate of the extraction medium per unit mass of thetobacco, there will occur, after the elapse of a time interval fromcommencement of the treatment process, a maximum difference between theextraction of the (greater) percentage amount of nitrosamines and the(lesser) percentage amount of nicotine. Thus it may be preferable todiscontinue the extraction treatment at or about this time.

[0023] A suitable mass flow rate of the supercritical fluid extractionmedium per kg of tobacco is in the range of about 1 kg/h to about 55kg/h, and is dependent on the process conditions, such as the tobaccopacking density in the chamber and the size of the chamber.Advantageously the mass flow rate of the supercritical fluid extractionmedium per kg of tobacco is in the range of 10 to 40 kg/h, moreadvantageously is in the range of 15 to 35 kg/h and is even moreadvantageously about 30 kg/h, although these figures do depend on whatthe desired product characteristics are.

[0024] Advantageously, the tobacco treated in accordance with theprocess of the present invention is cut tobacco, being cut lamina and/orcut stem tobacco. Alternatively, or in addition, the tobacco may be oneor more of whole leaf tobacco, tobacco dust and reconstituted tobacco.

[0025] If deemed appropriate, the tobacco treated in accordance with theprocess of the present invention may be subjected to a conditioningstep, whereby the moisture content of the tobacco, post-treatment, isbrought to less than about 15%, preferably less than 13%.

[0026] When it is the case that following treatment of tobacco with thesupercritical fluid, the nitrosamines are separated from thesupercritical fluid extraction medium by subjecting the medium to anitrosamine removal process, preferably the medium flows around a closedsystem.

[0027] Suitably, the closed system may comprise a first chamber, for thetreatment of the tobacco with supercritical fluid, and a second chamberin which the nitrosamine removal process takes place, wherein the firstand second chambers are interconnected by interconnecting means, pipe(s)for example. Such system further comprises fluid transfer means operableto cause the extraction medium to flow around the closed system. Anitrosamine removal material such as an ion-exchange resin or adsorbentmay reside in the second chamber, such that supercritical fluidextraction medium, following treatment of the tobacco therewith, istransferred via the interconnecting means to the second chamber, whereinnitrosamines are totally or substantially removed. The supercriticalfluid extraction medium, minus nitrosamines, may then be returned to thetobacco in the first chamber.

[0028] Suitably, a plurality of interconnected chambers may -be providedfor the treatment of the tobacco with supercritical fluid and/or aplurality of interconnected chambers may be provided for the nitrosamineremoval process. When it is the case that more than one chamber isprovided for either the treatment of the tobacco or the nitrosamineremoval process, or for both, the supercritical fluid may flowsequentially through the chambers.

[0029] Alternatively, the closed system may comprise a first or singlechamber having inlet and outlet means wherein interconnecting meansinterconnect the inlet with the outlet means of the chamber. Suitably,the interconnecting means may serve for the transfer of supercriticalfluid extraction medium, under the action of fluid transfer means, fromthe outlet means of the chamber to and through a nitrosamine removalprocess station to the inlet means of the chamber. Preferably, theamount of fluid in the interconnecting means is kept to a minimum. Anitrosamine removal material, such as an ion exchanger or an adsorbent,may be contained within any suitable permeable container so as toprovide a means by which fluid may pass through the container and ameans by which the tobacco is prevented from contact with thenitrosamine removal material.

[0030] Alternatively the nitrosamine removal process may, for instance,be constituted by the transfer of the medium through a UV light source.In this instance, the interconnecting means must be pervious to UWlight.

[0031] Suitably, a plurality of interconnected chambers may be providedfor the treatment of the tobacco with supercritical fluid.

[0032] In addition to subjecting the tobacco to treatment with thesupercritical fluid to extract nitrosamines from the tobacco, thetobacco may be subjected to a microbial deactivation process. As statedabove microbes, including Enterobacter agglomerans, Bacillus spp,Fusarium equisetti, Cladosporium cladosporoides, Altenaria alternata andAcremonium arxii are thought to be responsible for or contribute to theproduction of nitrosamines during curing of the tobacco. In fact, it isthought that microbes may also be a contributory factor in theproduction of nitrosamines in tobacco during storage of cured tobacco.Thus a reduction in microbial activity in the tobacco by way of themicrobial deactivation process reduces the likelihood of reformation ofnitrosamines in the tobacco post-extraction thereof. The microbialdeactivation process may be carried out before or after subjecting thetobacco to the treatment with the supercritical fluid. A furtheralternative is to subject the tobacco to treatment with thesupercritical fluid under microbial deactivating conditions, such thatmicrobial deactivation and extraction occur simultaneously.

[0033] Suitably, the microbial deactivation process may comprise apasteurisation process, wherein the tobacco is heated to a specifiedtemperature and maintained at that temperature for a set period of time.By way of example, the tobacco may be heated to a temperature in therange of about 70° to about 150° Celsius for a period of between about30 seconds to about 2 minutes. The heating may be effected by, forexample, convection heating by way of contacting the tobacco with agaseous heating medium, microwave heating or radio frequency heating.

[0034] Suitably, the moisture content of the tobacco being subjected tothe sterilisation process is adjustable by way of either a pre- or apost-conditioning step.

[0035] Alternatively, the treatment of tobacco with, for example,ionising radiation, UV radiation, freeze drying or an electron beam tokill microbes may be used as the microbial deactivation process.

[0036] In addition to the treatment of the tobacco with thesupercritical fluid to extract nitrosamines from the tobacco, thetobacco may also be subjected to a nitrite/nitrate removal process.Nitrites are important precursors of nitrosamines, whereas nitrates areprecursors of nitrites. It is thought that following nitrosamine removalresidual nitrites in the tobacco may be free to react with alkaloidsalso present in the tobacco thus to re-form nitrosamines. Thenitrite/nitrate removal process may suitably comprise the steps ofsolvent extraction to remove the nitrites/nitrates from the tobacco,followed by ion exchange to bind the nitrites/nitrates. Alternatively,the nitrites may be removed by way of an oxidation step. In a yetfurther alternative, removal of nitrites/nitrates using micro-organismsas disclosed in any one of GB 1 440 171, GB 1 585 024, U.S. Pat. No.4,709,710 or GB 2 014 031 may be used.

[0037] As with the microbial deactivation process, the nitrite/nitrateremoval process may be carried out before, after or during the treatmentof the tobacco with the supercritical fluid. When the nitrite/nitrateremoval process is carried out simultaneously with the treatment of thetobacco with the supercritical fluid, the process may in order to removenitrites from the tobacco comprise, for example, the step of eitherapplying ascorbic acid to the tobacco prior to treatment of the tobaccowith the supercritical fluid; incorporating ascorbic acid with thesupercritical fluid; or, when an ion exchanger or adsorbent material ispresent, incorporating ascorbic acid with the ion exchanger oradsorbent. The ascorbic acid has the effect of scavenging nitrites fromthe tobacco.

[0038] The nitrite/nitrate removal process may be carried out as analternative to or in addition to the microbial deactivation process.

[0039] The inventive process provides a Burley tobacco having an initialnitrosamine content after curing in the range of about 0.3 ppm—about 30ppm, which after processing has a nitrosamine content that is at least45% lower. If the tobacco is a Burley tobacco having a nitrosaminecontent of 5-6 ppm, after processing the content is preferably 3.6 ppmor less.

[0040] The inventive process also provides a Virginia tobacco having aninitial moisture content after curing of less than 8.5 ppm, which afterprocessing has a nitrosamine content that is at least 45% lower.

[0041] Preferably the Burley or Virginia processed tobacco have anitrosamine content of at least 60% lower than its original content.

[0042] The inventive process also provides a US blended tobacco havingan original nicotine content in the range of 0.10-2.0% and a nitrosaminecontent in the range of 0.10-1.2 μg/g which after processing has apercentage decrease in nitrosamines to percentage decrease in nicotinein the range of 1:1 to 10:1.

[0043] The inventive process also provides a Virginia blended tobaccohaving an original nicotine content in the range of 0.30-2.15% and anitrosamiine content in the range of 0.10-1.5 μg/g, which afterprocessing has a percentage decrease in nitrosamines to percentagedecrease in nicotine in the range of 1:1 to 10:1.

[0044] Preferably the ratio is in the range of 5:1 or more, and morepreferably 8:1 or more.

[0045] In order that the present invention may be clearly understood andreadily carried into effect reference will now be made, by way ofexample, to the accompanying diagrammatic drawing, in which:-

[0046]FIG. 1 shows an apparatus for carrying out a process according toa first aspect of the present invention; and

[0047]FIG. 2 shows an apparatus for carrying out a process according toan alternative aspect of the present invention.

[0048] The apparatus as shown in FIG. 1 is a closed system comprising afirst chamber 1 and a second chamber 2 wherein the first and secondchambers 1, 2 are interconnected by interconnecting pipes 3. The closedsystem further comprises fluid transfer means, namely a pump 4. Theapparatus further comprises a reservoir tank 5 interconnected with thefirst chamber 1 via a duct 6. Valve 7 is located in duct 6 which valve 7is operable to close the tank 5.

EXAMPLE 1

[0049] In operation of the FIG. 1 apparatus, about 30 kg of cut tobaccohaving a moisture content of either about 14% or 25% (see Table 1) isplaced in the first chamber 1, the chamber having a volume of 1501. Anion exchanger, namely an acidic ion exchange resin (as available fromBayer GmbH) having a weight of 4.4 kg, is placed into the second chamber2, the chamber having a volume of 1501. The ion exchanger is mixed withabout 500 g of solid potassium citrate granules. The reservoir tank 5 ischarged with carbon dioxide, which carbon dioxide is then pressurised bypump means (not shown) and is transferred by the pump means from thereservoir tank 5 to the first and second chambers 1, 2 and theinterconnecting pipes 3 until the requisite extraction conditions areachieved, namely a pressure of about 250 bar and a temperature of about70° Celsius. At this point the carbon dioxide reservoir tank is closedby closing valve 7. The supercritical carbon dioxide is then circulated,under the action of the pump 4, through the first chamber 1 (and,therefore, through the tobacco contained therein) and through the secondchamber 2 (and, therefore, through the ion exchange resin therein) viathe interconnecting pipes 3. The supercritical carbon dioxide extractionmedium is circulated about the closed system for a period of either 1.5hours or 3 hours. Then the first and second chambers 1, 2 aredecompressed by opening vent means (not shown) and the chambers areopened.

[0050] The nicotine and nitrosamine contents of the thus treated tobaccoare then evaluated using suitable standard laboratory tests.

[0051] Such a tobacco extraction process has been found to remove asubstantial proportion of tobacco specific nitrosamines from the treatedtobacco. Table 1 discloses percentage reductions in the tobacco of bothnicotine and nitrosamines following treatment of the tobacco as outlinedabove. The total amount of CO₂ used for these examples was 2109 kg.TABLE 1 Nicotine Nitrosamines Tobacco Extraction Reduction Reduction RunNo. m.c. Period (h) (%) (%) 1 14% 1.5 67 90 2 14% 3.0 78.5 94 3 25% 1.565.5 93.5 4 25% 3.0 77 95

[0052] Treatment for 1.5 hours results in a greater difference betweenthe percentage amount of nitrosamines and the percentage amount ofnicotine extracted, as compared with treatment for 3 hours.

EXAMPLE 2

[0053] It was believed that the extraction period outlined above couldbe reduced further without substantially affecting the percentagereduction of nitrosamines, whilst further reducing the percentagereduction of nicotine. For instance, the extraction period may bebetween about 15 minutes to about 1.5 hours, preferably between about 20minutes to about 1 hour, more preferably between about 25 minutes toabout 40 minutes and even more preferably about 30 minutes.

[0054] The conditions of extraction are preferably further biasedtowards the extraction in the supercritical fluid of nitrosamines, ascompared with other tobacco specific compounds, such as nicotine.Several other methods of biasing the extraction towards nitrosamineremoval, as compared with other tobacco specific compounds, may be usedin addition to or separately from adjustment of the extraction period.For instance, the pH of the tobacco may be maintained at less than about6.5, preferably about 5.5. In accordance with a further alternative, thesupercritical fluid extraction medium may be saturated, or substantiallysaturated, with tobacco specific compounds, or commercially availablechemical analogues thereof, other than nitrosamines before contactingthe extraction medium with the tobacco treatment. A yet furtheralternative, when the supercritical fluid is carbon dioxide, may be tocool the tobacco to a temperature below about 35° C., such that when thesupercritical carbon dioxide is pumped into the chamber containing thetobacco the general effectiveness of the extraction process is reducedwith preferential bias against the removal of tobacco specific compoundsother than nitrosamines. Biasing towards the extraction of nitrosaminesmay also be effected by altering (i.e. increasing) the packing densityof the tobacco in the extraction chamber.

[0055] Furthermore, biasing may be effected by altering, i.e. loweringthe mass flow rate of the supercritical fluid extraction medium per unitmass of tobacco. For example, reducing the flow rate of thesupercritical fluid per kg of tobacco to less than 30 kg/h. Each of theabove outlined methods of biasing the extraction towards nitrosamineremoval, as compared with other tobacco specific compounds, may becarried out separately or in various combinations with one another.

[0056] As an optional addition to the above described process, the ionexchange resin situate in the second chamber 2, following decompressionof the closed system, is flushed or washed with water. The washings arethen treated with UV light from a UV light source (not shown). Exposureof the washings to UV light results in the degradation of nitrosaminesin the washings. Extract(s) other than nitrosamines in the washings isthen re-incorporated with the tobacco. Other extract(s) may include, forexample, nicotine and/or flavour substances. In this way, the end resultis that nitrosamines are selectively removed from the tobacco, withoutadversely affecting the taste of the tobacco.

[0057] Some examples of the above described variations are disclosed inTable 2 below.

[0058] In view of the variability of nicotine and nitrosamine contentsin each batch of tobacco, 300 g from each batch was retained as acontrol for the batch. The nicotine and nitrosamine levels for eachcontrol from the 4 batches sampled are given in Table 3 below. TABLE 2Total Nicotine % TSNA in Other Trial/ Tob type in blend nicotine blend %TSNA Extraction Total process run & wt % reduction μg/g reduction timeCO₂ kg variables 1 run 2 238/ 0.53 78.46 0.14 94.33   3 hrs 2190 15%moist 35 kg tobacco 1 run 4 238/ 0.56 77.24 0.12 95.14   3 hrs 2190 25%moist 35 kg tobacco 1 run 5 238/ 0.33 86.59 0.15 93.93   3 hrs 2190 500g Citrate 35 kg added to ion exchanger 1 run 7 USB/ 0.17 91.58 0.1297.12   3 hrs 2190 15% moist 35 kg tobacco 1 run 9 USB/ 0.14 93.07 0.2095.20   3 hrs 2190 25% moist 35 kg tobacco 4 run 1 USB/ 1.47 20.11 1.1361.69   2 hrs 40 At original pH  3 kg (5.44) 4 run 3 USB/ 1.7 7.61 1.0863.39   2 hrs 40 pH of tobacco  3 kg reduced (4.1- 4.3) 4 run 4 238/1.96 14.78 0.72 70.49   2 hrs 40  3 kg 4 run 6 238/ 2.12 7.83 1.36 44.26  2 hrs 10  3 kg 3 run 11 238/ 2.1 8.7 0.65 73.36  15 mins 200 15 kg 5run 3 USB/ 1.4 22.65 1.11 66.57 2.5 hrs 40 Glass beads, no  3 kg ionexchanger

[0059] TABLE 3 Nicotine Content (%) Nitrosamine Content (μg/g) Batch No.USB 238 USB 238 1 2.02 2.46 4.17 2.47 4 1.84 2.30 2.95 2.44 3 1.84 2.292.95 2.44 5 1.77 not 3.32 not reported reported yet yet

EXAMPLE 3

[0060] The apparatus shown in FIG. 2 is also a closed system, whichapparatus comprises a chamber 1 provided with an inlet 8 and an outlet9, interconnecting pipe 10, wherein the pipe 10 interconnects the inlet8 with the outlet 9 of the chamber 1, and fluid transfer means, i.e. apump 4. This apparatus further comprises a reservoir tank 5interconnected with the chamber 1 via a duct 6. Valve 7 located in duct6 allows for tank 5 to be closed. Adjacent a position of the pipe 10 islocated a UV light source.

[0061] In operation of the FIG. 2 apparatus about 100 kg of cut tobaccohaving an appropriate moisture content is placed into chamber 1. Thereservoir tank 5 is charged with carbon dioxide, which carbon dioxide isthen pressurised by pump means (not shown) and is transferred by thepump means from the reservoir tank 5 to the chamber 1 and pipe 10 untilthe requisite extraction conditions are achieved, namely a pressure ofabout 250 bar and a temperature of about 50° Celsius. Then the tank 5 isclosed by closing the valve 6. The supercritical carbon dioxide is thencirculated, under the action of the pump 4, through the chamber 1 (and,therefore, through the tobacco contained therein) and through the pipe10. The UV light source 11 irradiates the supercritical carbon dioxideextraction medium in the pipe 10. Thus, nitrosamines in thesupercritical carbon dioxide are degraded. Degradation products thereofmay then be removed, for instance by passing the supercritical carbondioxide through a metal mesh (not shown). The pipe 10 is comprised of,at least in the region of the UV light source 11, material which ispervious to UV light, e.g. a high pressure quartz window. The amount ofsupercritical carbon dioxide in the interconnecting pipe 10 is kept to aminimum by use of a pipe 10 having a bore of a small diameter (i.e. adiameter of about 1 cm). The supercritical carbon dioxide is, followingexposure to the UV light, returned to the chamber 1 and again intocontact with the tobacco therein. The supercritical carbon dioxide iscirculated for a period of 30 minutes. Then the chamber 1 and the pipe10 are decompressed by opening vent means (not shown). The tobaccotreated in this way is free, or substantially free, of nitrosamines,whilst the nicotine content of the tobacco remained substantially thesame pre- and post-treatment.

[0062] A further alternative apparatus (not shown) comprisessubstantially the apparatus shown in FIG. 2 with a nitrosamine removalmaterial held within a fluid permeable container in the chamber 1. Thefluid may be re-circulated through the system for a number of timesbefore removal and optional subsequent removal of nitrosaminestherefrom.

1. A tobacco treatment process wherein tobacco is subjected to treatmentwith a supercritical fluid extraction medium to extract nitrosaminesfrom said tobacco.
 2. A process according to claim 1, whereby saidnitrosamines are separated from said supercritical fluid extractionmedium by subjecting said extraction medium to a nitrosamine removalprocess.
 3. A process according to claim 2, wherein said nitrosamineremoval process comprises a chemisorption step.
 4. A process accordingto claim 3, wherein said chemisorption step comprises the use of an ionexchanger.
 5. A process according to claim 2, wherein said nitrosamineremoval process comprises an adsorbent step.
 6. A process according toclaim 5, wherein an adsorbent of said adsorbent step is selected fromone or more of the group consisting of glass beads, activated charcoal,aluminium silicate and zeolites.
 7. A process according to claim 2,wherein said nitrosamine removal process comprises treatment of saidextraction medium with ultraviolet (UV) light.
 8. A process according toclaim 2, wherein said nitrosamine removal process comprises eitherprecipitation of said nitrosamines from said extraction medium, orsubjecting said extraction medium to nitrosamine-specific enzymebreakdown, or chromatographic separation of said nitrosamines from saidextraction medium.
 9. A process according to any one of claims 2-8,wherein said nitrosamine removal process comprises a plurality ofremoval processes.
 10. A process according to any one of claims 2-9,wherein following said nitrosamine removal process, said extractionmedium, being wholly or substantially free of said nitrosamines, isbrought into contact with the tobacco, such that extract(s) other thannitrosamines in said extraction medium may be incorporated orre-incorporated with said tobacco.
 11. A process according to claim 10,wherein said extract(s) comprise nicotine and/or flavour substances. 12.A process according to any one of the preceding claims wherein saidsupercritical fluid extraction medium is supercritical carbon dioxide.13. A process according to any one of the preceding claims, wherein anacid is added to said tobacco prior to treatment of said tobacco withsaid supercritical fluid; or to said supercritical fluid prior totreatment of said tobacco with said supercritical fluid.
 14. A processaccording to any one of claims 4 or 5 when appended to claim 3, whereinan acid is added to the ion exchanger or adsorbent.
 15. A processaccording to any one of claims 1-14, wherein one or more of an organicsolvent or an alcohol is added in addition to, or alternatively of, saidacid.
 16. A process according to claim 15, wherein said acid is anorganic acid.
 17. A process according to claim 16, wherein said acid isan organic acid selected from one or more of the group consisting ofmalonic acid, ascorbic acid, succinic acid, glutanic acid, adipic acid,malic acid, tartaric acid, mucic acid and citric acid, or a saltderivative thereof.
 18. A process according to claim 17, wherein saidorganic acid is a citric acid salt.
 19. A process according to claim 18,wherein said citric acid salt is potassium citrate.
 20. A processaccording to any one of the preceding claims, wherein said extraction ofsaid nitrosamines from said tobacco with said supercritical fluid takesplace at an elevated pressure and temperature.
 21. A process accordingto claim 20, wherein when supercritical fluid is supercritical carbondixoide, said pressure is in the range of 100 to 350 bar.
 22. A processaccording to claim 21, wherein said pressure is about 200 to 300 bar.23. A process according to claim 22, wherein said pressure is about 240to 260 bar.
 24. A process according to any one of claims 20-23, whereinsaid temperature is greater than about 35° Celsius.
 25. A processaccording to claim 24, wherein said temperature is an a range of about35° to about 140+ Celsius.
 26. A process according to claim 25, whereinsaid temperature is in a range of about 35° to about 90° Celsius.
 27. Aprocess according to any one of the preceding claims, wherein saidtobacco is placed in a closable chamber or bomb during said extractiontreatment thereof with supercritical fluid.
 28. A process according toany one of claims 20 to 27, wherein said elevated temperature iseffected by heat transfer or by electromagnetic radiation.
 29. A processaccording to any one of the preceding claims wherein no, or very little,nicotine is removed from said tobacco in said extraction medium.
 30. Aprocess according to any one of the preceding claims, wherein the pH ofsaid tobacco is less than about 6.5.
 31. A process according to claim30, wherein said pH of said acid is less than about 5.5.
 32. A processaccording to any one of the preceding claims, wherein the ratio of thepercentage reduction in nitrosamines to the percentage reduction innicotine is in the range of about 1.1:1 to about 18:1.
 33. A processaccording to claim 32, wherein said ratio is in the range of about 1.3:1to about 10:1.
 34. A process according to claim 33, wherein said ratiois in the range of about 2:1 to about 6:1.
 35. A process according toany one of the preceding claims, wherein a suitable mass flow rate ofsaid supercritical fluid extraction medium per kg of tobacco is about1-55 kg/h.
 36. A process according to claim 35, wherein said mass flowrate is in the range of 10-40 kg/hr.
 37. A process according to claim36, wherein said mass flow rate is in the range of 15-35 kg/hr.
 38. Aprocess according to claim 37, wherein said mass flow rate is about 30kg/h.
 39. A process according to any one of the preceding claims,wherein said tobacco treated in accordance with said process is cuttobacco and/or whole leaf tobacco, tobacco dust or reconstitutedtobacco.
 40. A process according to any one of the preceding claims,wherein said tobacco is subjected to a microbial deactivation process.41. A process according to claim 40, wherein said microbial deactivationprocess comprises a pasteurisation process.
 42. A process according toclaim 41, wherein said tobacco is heated to a temperature in the rangeof about 70° C. to about 150° C. for a period of between 30 seconds to 2minutes.
 43. A process according to claim 41, wherein saidpasteurisation process is effected by heating of said tobacco byconvection heating by way of contacting said tobacco with a gaseousheating medium, by microwave heating or by radio frequency heating. 44.A process according to any one of claims 40-43, wherein the moisturecontent of said tobacco being subjected to said microbial deactivationprocess is adjustable by way of either a pre- or post-conditioning step.45. A process according to claim 41, wherein said microbial deactivationprocess comprises use of ionising radiation, UW radiation, freeze dryingor an electron beam.
 46. A process according to any one of claims 1-45,wherein said tobacco is subjected to nitrite/nitrate removal process,before, during or after treatment of said tobacco with saidsupercritical fluid.
 47. A process according to claim 46, wherein saidnitrite/nitrate removal process comprises the steps of solventextraction to remove nitrites/nitrates from said tobacco followed by ionexchange to bind said nitrites/nitrates.
 48. A process according toclaim 46, wherein said nitrite removal process comprises an oxidationstep or use of micro-organisms.
 49. A process according to any one ofclaims 46-48, wherein ascorbic acid is applied to said tobacco,incorporated with said supercritical fluid, or incorporated with achemisorption medium.
 50. A nitrosamine extraction apparatus in useaccording to any one of the preceding claims, said apparatus being aclosed system comprising a first chamber for the treatment of saidtobacco with supercritical fluid, a second chamber in which saidnitrosamine removal process takes place, said chambers beinginterconnected by interconnecting means, said apparatus furthercomprising supercritical fluid supply means supplying supercriticalfluid, fluid transfer means operable to cause said supercritical fluidto flow around said closed system, and a nitrosamine removal materialresiding in said second chamber.
 51. Apparatus according to claim 50,wherein said fluid transfer means is a pump.
 52. Apparatus according toclaim 50, wherein said fluid transfer means is a pressure differentialsystem.
 53. Apparatus according to any one of claims 50-52, wherein aplurality of interconnected chambers are provided for said treatment ofsaid tobacco with supercritical fluid and/or a plurality ofinterconnected chambers are provided for said nitrosamine removalprocess.
 54. Apparatus according to claim 53, wherein said supercriticalfluid flows sequentially through said chambers.
 55. A nitrosamineextraction apparatus in use according to any one of claims 1-49, saidapparatus being a closed system, wherein said closed system comprises achamber having inlet and outlet means connected by interconnectingmeans, fluid transfer means and nitrosamine removal means.
 56. Apparatusaccording to claim 55, wherein said nitrosamine removal means comprisesan ion exchanger or an adsorbent held in a supercritical fluid permeablecontainer within said chamber.
 57. A closed system according to claim56, wherein said interconnecting means serve for the transfer ofsupercritical fluid extraction medium under the action of fluid transfermeans, from said outlet means of said chamber and through a nitrosamineremoval process station to said inlet means of said chamber.
 58. ABurley tobacco having an initial nitrosamine content after curing in therange of about 0.3 ppm—about 3.0 ppm, wherein said Burley tobacco has anitrosamine content that is at least 45% lower following treatmentaccording to the process of any one of claims 1-49.
 59. A Virginiatobacco having an initial nitrosamine content after curing less than 8.5ppm, wherein said Virginia tobacco has a nitrosamine content that is atleast 45% lower following treatment according to the process of any oneof claims 1-49.
 60. A Burley or Virginia tobacco according to claim 59or 60, wherein said nitrosamine content is at least 60% lower than theoriginal content.
 61. A Burley tobacco having an initial nitrosaminecontent of 5-6 ppm, the nitrosamine content after treatment according toany one of claims 1-49 being 3.6 ppm or less.
 62. A US blended tobaccohaving an original nicotine content in the range of 0.10-2.0% and anitrosamine content in the range of 0.10-0 1.2 μg/g, wherein said blendafter processing according to any one of claims 1-49 has a ratio ofpercentage decrease in nitrosamines to percentage decrease in nicotinein the range of 1:1 to 10:1.
 63. A Virginia tobacco blend having anoriginal nicotine content in the range of 0.10-2.0% and a nitrosaminecontent in the range of 0.10-1.2 μg/g, wherein said blend afterprocessing according to any one of claims 1-49 has a ratio of percentagedecrease in nitrosamine to percentage decrease in nicotine in the rangeof 1:1 to 10:1.
 64. A tobacco blend according to claim 62 or 63, whereinsaid ratio is preferably 5:1 or more.
 65. A tobacco blend according toclaim 62 or 63, wherein said ratio is preferably 8:1 or more.
 66. Atobacco treatment process substantially as hereinabove described withreference to FIGS. 1 and 2 hereof.